Blade sharpening machine



Filed March 9, 1954 FIG. l.

E i/O Patented Apr. 21, 1936 UNITED STATES PATENT OFFICE 6 Claims.

The present invention relates to a machine for grinding the blades of lawn mowers and for similar purposes, and it has for its object to produce a machine for this purpose that is simple in construction, that is capable of accurate grinding and sharpening of the blades of such machines, which is self-contained and portable in its nature, and has novel features of construction that will be herein described.

In the accompanying drawing, wherein the preferred embodiment of the present invention is illustrated,

Figure 1 is a perspective embodying the invention;

Figure 2 is a vertical sectional view taken on the line 2-2 of Figure 1; and

Figure 3 is a View similar to Figure 2 illustrating a different adjustment of the parts of the machine whereby a different bevel is imparted to the blade from that given when the parts are arranged as shown in Figure 2.

view of a machine The machine illustrated in the drawing comprises a supporting open frame, most of the parts of which may be, and preferably are, formed of angle iron. Such frame consists of four corner posts or angles, 2, upper and lower longitudinal side bars, 3 and 3, upper and lower cross end bars, 4 and 4', and intermediate stationary mem-.

bers 5 arranged to support operative and moving parts of the machine. This frame is preferably supported upon casters 6 arranged respectively below the corner posts 2.

Mounted in the intermediate supporting members 5 and near one end of the frame is a driven shaft 1 upon which are mounted pulleys 8.

9 indicates a motor, an electric motor being represented, which may be connected with one of the pulleys 8 by belt l0.

To the inner end of the shaft 1 is connected a chuck l I, such as an ordinary drill chuck, into which may be inserted and secured the shaft 38 of a lawn mower reel, the blades 39 of which are to be ground or sharpened. At the other end of the frame and in line with the driven shaft 1 is mounted a stub shaft l3 which also is provided with a chuck l2 to receive an end of the shaft 38.

Supported in the longitudinal bars 3 and 3, near that end of the frame in which is mounted the driven shaft 1, is a vertical shaft l4 serving as, a support for a bracket l5 upon which is mounted the motor 9. The bracket is formed with bearings l6 encircling the shaft and is provided with one or more locking bolts I! by which the bracket may be secured in desired position, as for driving the shaft 1.

I9 is another vertical shaft supported in longitudinal members 3 and 3' of the frame and located preferably about opposite to the shaft I4. It carries at its upper end a grinding wheel or disk It and is provided with a pulley 20 connected by belt 2! with one of the pulleys 8, from which the shaft receives power to rotate it and turn the grinder l8.

22 indicates a stool or seat supported at the end of an upright shaft 22' which is'connected with the frame of the machine by swinging bracket 23 formed of two members pivotally connected respectively with the upper and lower longitudinal side bars on that side of the frame, preferably, where is the grinder l8. The lower end of the shaft 22 may be provided with a foot to rest upon the floor, or with a caster 24 as represented.

At each corner of the frame, preferably within the angle of a corner post 2, is mounted a vertical shaft 25, such shafts being preferably screw threaded near their lower ends and their upper exposed ends being shaped to receive a wrench by which they may be turned. The lower ends of these shafts 25 are seated in nuts 28 securely supported in the framework so that the shafts may be adjusted longitudinally. Upon each'pair of shafts 25 at an end of the machine is mounted a cross end piece 26 supported so as to be free to move vertically along the shafts. Surrounding each shaft 25 are two coil springs 21, 21, one located above and the other below the floating cross end piece 26. A second floating end piece 33, one at each end of the machine, is located directly above the piece 26, and supported upon the two end vertical shafts 25', resting upon the upper ends of the upper springs 21 and located just below an upper cross end frame bar 4. The springs 21 are of sufficient resistance to longitudinal compression to insure that the central, floating cross bars 26.shal1 be held in their desired intermediate positions with sufficient force for the purposes of the present invention and yet shall be yieldingly supported, in both directions. For insuring good working conditions each spring 25 is fitted at each end with a combined washer and guide which, however, it is not deemed necesary to illustrate.

Carried by the central floating end pieces 26 are a pair of longitudinal bars 29 that constitute a guide and support for the grinder employed in sharpening the cutting blades of the lawn mower. Mounted upon these bars so as to be free to move longitudinally thereon is a sliding clamp 30 constructed to hold and properly secure a grinding block 3| of carborundum or other suitable material that serves as the grinder for the blades 39. The clamp is provided on its exposed upper side with;,a handle 32 by which the grinder may be manipulated back and forth along the slide bars 29 in the grinding operations.

In each upper cross frame piece 4 are mounted a pair of screw rods 34 provided with cranks 35 for manipulation and with bearing pieces 40 that rest upon the upper, floating cross pieces 33.

Upon each corner post 2 there is preferably arranged a scale 36 adjacent to which scales move pointers 3'! carried respectively by the intermediate floating end pieces 26 and '33.

The operation of the machine which has been described is as follows:

The reel of a lawn mower, the knives of which are to be ground, is secured, between the shafts I and I3, so as to be turned when the motor is driven. This having been accomplished the frame carrying the grinder 3| is properly adjusted relative to such reel and its knives.

This is accomplished through manipulation of the screw shafts 25 and the screws 34. Turning the screw shafts to raise them, without at the same time adjusting the screws 34 results in raising the grinder guide 29 and increases the tension upon the springs 21 that yieldingly hold the guide in position. If that tension is too great it may be relieved by raising, that is allowing it to rise, the bar 33, through proper manipulation of the screws 34. By turning one screw so that its foot or bearing 40 resting on the bar 33 is below that of the other foot at the same end of the machine, the cross bar 33 is inclined out of the horizontal, and the springs 21 surrounding those vertical shafts 25 at the lowered end of the bar 33 are compressed, and this in turn causes the intermediate cross bar 23 and with it the grinder guide 29 to be inclined. In this way the grinder is so set with reference to the blades 39 as to grind the latter at the desired level. In grinding the cutting blades carried by the reel of a lawn mower of common construction, by the use of a machine such as has been described, it has been found very advantageous to first adjust the grinder 31 at an angle so that the reel being driven in a clockwise direction, the front or advancing edges of the knives will be ground off uniformly and accurately. Then the grinder may be tilted in the opposite direction and the reel driven anticlockwise so that the blades will be sharpened at an angle to the edge which has already been formed by the grinding just before described. These adjustments may be easily and accurately secured through proper manipulation of the screws 25 and 34, and to assist the operator in making the adjustments, and to enable him to adjust both ends of the grinder guideway alike, the scales 36 and pointers 31 are provided.

When the grinding machine is not in use the motor may be swung on its shaft l4 so as to be within the confines of the open supporting frame; and the stool 22 likewise swing so as to be close to the machine. With these parts closely folded against or into this frame, the whole machine may be moved to a position in the shop where it will be out of the way until it is again desired to use it. The machine is thus complete and self-contained, is easily portable and is capable of being compactly folded for storage when not in use.

What I claim is:

1. In a machine for grinding the cutting blades of lawn mower reels and the like, the combination of means for revolving the reel, a grinder for acting on the blades of the reel, a guide by which the grinder is supported and on which it is movable back and forth on straight lines; and means for supporting the guide yieldingly so that the grinder may have the desired pressure contact upon the blades and means for changing the angle of the guide so as to cause the grinder tohave varying angular relation to the reel accordingly as the guide is adjusted.

2. In a grinding machine for lawn mower blades and the like, the combination with a supporting frame, of means for revolving the blade to be sharpened, a grinder, a longitudinally arranged guide for the grinder disposed parallel with the axis of revolution of the blade, end bars mounted in the frame supporting the guide at its ends, springs arranged to hold the opposite ends of the bars yieldingly and means for adjusting the springs so that tension applied thereby to the floating bars at one end or side of the machine shall be different from that at the other end or side to adjust the angle of the grinder to the blade, at will.

3. The combination stated in claim 2, including also scales on the frame to aid in accurate adjustments of the position and angular relation of the guide for the grinder.

4. In a grinding machine for lawn mower blades and the like, the combination with a supporting frame, of means for revolving the blade to be sharpened, a grinder, a longitudinally arranged guide for the grinder disposed parallel with the axis of revolution of the blade, end bars supporting the guide at its ends, rods passing loosely through said end bars near their ends, a pair of springs arranged on each of said rods and bearing on the said end bars one from above and one from below, and means whereby the tension of the springs of each rod may be varied independently.

5. In a grinding machine for lawn mower blades and the like, the combination with a supporting frame, of means within the frame for supporting and revolving the blade to be sharpened, a grinder, a longitudinally arranged guide for the grinder disposed parallel with the axis of revolution of the blade, floating bars mounted in the frame supporting the guide at its ends, rods mounted in the frame and passing loosely through said end bars near their ends, the rods being longitudinally adjustable, a pair of springs arranged on each of said rods and bearing on the said end bars one from above and one from below, floating cross bars mounted upon certain of the springs, such as the upper sets, and screw adjusting devices whereby the position of the said floating cross bar may be adjusted relative to the cross bars supporting the guide.

6. A self-contained portable grinding machine for lawn mower blades and the like comprising an open frame, a motor for rotating the blades to 

